A process of manufacturing a semiconductor device includes a process of removing only a peripheral edge portion of a film formed on the surface of a substrate (e.g., a semiconductor wafer) by wet etching, and this process is called bevel etching. In Japanese Patent Laid-Open Publication No. 2008-47629 (“Patent Document 1”), the bevel etching is performed by supplying an etching liquid to the peripheral edge portion of the surface of the substrate on which a film having one layer is formed. When a film having two (or more) layers is formed on the substrate to be subjected to the bevel etching, it may be requested to remove only the upper layer film while leaving the lower layer film. In this case, when a chemical liquid having a high etching selection ratio of the upper layer to the lower layer does not exist, it is difficult to implement the request.
For example, in an Si substrate on which an SiGe film as an upper layer is formed on an SiO2 film as a lower layer by a single-wafer CVD apparatus, the film thickness of the SiGe film in the vicinity of the edge of the substrate tends to be thin (see, e.g., FIG. 4A). Hence, at the wet etching time, the SiGe film in the vicinity of the edge is lost early, and the SiO2 film is exposed. When the etching is continued until the SiGe film is completely removed from the entire peripheral edge portion of the substrate, the SiO2 film in the vicinity of the edge is lost, and Si as a base may be exposed.
In addition, for example, in an Si substrate on which a poly-Si film as an upper layer is formed on an SiO2 film as a lower layer by a batch type film forming apparatus, the poly-Si film is formed on the entire surface of the substrate with a substantially uniform film thickness (see, e.g., FIG. 6A). In this substrate, the poly-Si film on the peripheral edge portion of the front surface and the entire rear surface of the substrate is removed. At this time, the poly-Si film in the vicinity of the edge which is etched by both a chemical liquid supplied for etching of the peripheral edge portion of the front surface and a chemical liquid supplied for etching of the rear surface may be lost early, and the SiO2 film as a base may also be lost.